In recent years, a data updating frequency in an ECU (Engine Control Unit) mounted in a vehicle is expected to increase as driving support functions of a vehicle increase. On the other hand, there is an in-vehicle security problem, and it is also desired a remote data update in the ECU at a higher security level. As one of such data updating methods of the ECU, there is a method of downloading data via a wireless line and installing the data in the ECU. In a conventional wireless data update, a password acquired by a user is input to a target vehicle using an input device, and transmitted from the vehicle to a server. Then, the data update is performed after authentication in the server.